Rebuilt cam failure lifespan

[SHO#7]

For the folks who have rebuilt cars that were once cam failures. What life can be expected. If the valves strike the pistons during failure and it bends the valves. Can one expect for a short life of the connecting rod bearings. I realize that is one lets go at 70 MPH the damage will be more than just idle. However, lets say one lets go at idle. It is rebuilt with a new cam and valves. Should the botom end of the motor have a good strong life left?

Thanks
Mike

 

[T-bird<SHO]

i was kinda wondering the same thing. i have a 98 and the cams are NOT welded although it appears to have had a head change prior to me getting the car. as these interference engines?

 

[MotorMouth]

are these interference engines?

Yes.........

 

[HotRodKid]

basicly, if the valves didnt damage the face of the pistons, then they didnt damage the con-rod bearings,

as its easier to dig the EDGE of a valve into a piston then it is to damage a con-rod bearing by pushing it tight against the crank

that being said, replacing the con-rod bearings during the rebuild is cheaper then replacing EVERYTHING if a rod should happen to come apart later on, cheap insurance is always a good thing

are these interference engines?

yes, thats why cam failure is such a bad deal

 

[naval-avi8or]

For the folks who have rebuilt cars that were once cam failures. What life can be expected. If the valves strike the pistons during failure and it bends the valves. Can one expect for a short life of the connecting rod bearings. I realize that is one lets go at 70 MPH the damage will be more than just idle. However, lets say one lets go at idle. It is rebuilt with a new cam and valves. Should the botom end of the motor have a good strong life left?

Thanks
Mike

When two objects collide with force something must give ie. bent valve, hole/damaged piston, bent conecting rod would be much more lickley than damage to a connecting rod bearing. If you were going to rebuild a cam failed engine at a minimuim you would want to replace any piston and connecting rod that shows signs of contact. Even if to the eye it looks ok the energy had to be disipated somewhere and will leave a week link to you motor down the road. Rod and main bearings are cheap replace them while you have the chance.

 

[E1]

Oh heavens. Make a gauge.
Take a piece of metal that is rigid and big enough to span across the cylinder and bolt down to the block. Drill it out as necessary so you can bolt it down to the head deck make sure to deburr the drill holes so the plate lays flat. Drill and tap the center area of the plate with a fairly small size thread - #10 x 32 is a good size - and put a screw through it with a jam nut on top of the plate.

Bolt this over any cylinder and hand crank the engine until the piston is at TDC (top dead center). Screw the bolt down by hand until it touches the piston, lock the screw in place with the jam nut. Move the plate to the next cylinder and crank the engine around. ALL 4 pistons MUST reach the bolt at the same TDC or you have a bent rod on the one that stops low.

Get it?

 

[Mr Anonymous]

We've seen a number of rebuilt cam failure motors with over 100K since the rebuild now. I'm thinking Randy must have at least 80K or so on his, maybe he'll chime in.

A properly inspected and rebuilt cam failure motor should be better than one that came from the factory (in that it won't fail from cam failure).

As long as I knew who rebuilt it and had confidence in their work, I wouldn't think twice about it (although last time I checked Jasper was still pinning their rebuilds, which I'd either recommend getting welded or at least paying Jasper for the super-duper-extended warranty).

 

[SHOZ123]

Rod bearings are cheap. Any time the bottom of the motor is available and it's been 50k might as well or if you suspect for any other reason.